The study notes that the most common non-dope ingredients in street heroin are lactose, milk sugar, sucrose, cellulose, mannitol and other inert ingredients, but there is an increasing trend for heroin to contain psychoactive chemicals or additional substances to alter its effect through changing how it is absorbed into the body.

Interestingly, the paper also notes that professional heroin cutters are expensive, charging up to $20,000 for a kilo of heroin. This is likely due to the skill and knowledge needed to select ingredients that will have certain effects, which can be different for ‘smokers’, ‘snorters’ and ‘injectors’.

Ingredients that affect the vaporisation point of heroin will be more important for smokers, while adulterants that increase absorption through the nasal passages will obviously be more important for snorters.

For injectors, cutters need to be able to select ingredients that aren’t going to gum up needles or cause too much damage to the users’ veins.

Additionally, some ingredients are added purely for their psychoactive effect to give a different experience and ‘brand’ the dope.

However, owing to the cost of a professional cutter, some dealers just cut it themselves with whatever they think is reasonable, meaning all kinds of potentially fatal ingredients end up in the average bag of smack.